Rendering realistic 3D images in a computer graphics development environment requires numerous computations and calculations to effectively model real-world lighting conditions and the physical properties of objects to be rendered. For example, an image of a creature in an animated motion picture may involve multiple light sources and the physical properties of the creature may exhibit various qualities such as transparency, reflection, refraction, translucency, and the like.
In general, modeling a highly realistic 3D object involves, among other things, determining both the direct surface scattering and the subsurface scattering contributions for all points on the object, and then combining those direct and subsurface scattering contributions to create a final image of the object. Consequently, modeling the subsurface scattering characteristics of 3D objects, especially those composed of translucent materials, is a crucial component in the look of 3D objects in many computer graphic generated feature films. For example, rendering realistic-looking skin for photo-real digital doubles or other creatures typically involves the use of a rendering technique that captures the subsurface scattering effects of the creatures' skin. In cinematic-quality rendering, one widely-used technique is described in “A Rapid Hierarchical Rendering Technique for Translucent Materials” published in SIGGRAPH 2002 by Henrik Wann Jensen and Juan Buhler.